Poor late Mike, the old short-haired dog and the most needy for cold weather protection, didn't live to enjoy the new doghouse. Our other dog Zero, although older at 16 years, has plenty of thick hair and is actually energized by the cold. She will probably seldom use the shelter.
I'll still do a doggy door entrance, but now I'm calling it a greenhouse.
Besides the doggy door and a well insulated area for dogs to sleep, I started with two other requirements, a curved top made from metal electrical conduit and a storm door human entrance. The curved top would allow the versatility of using either plastic sheeting or plastic panels and, in the summer, shade fabric. I planned to re-cycle an old storm door for the entrance. I also wanted the house mounted on skids so I could build it in my garage and later move it around the yard. The width, six feet, was set by the diameter of a curved ten foot piece of conduit. The length of eight feet was constrained to the dimensions of plywood for convenience.
The first step was to see if I could successfully bend an electrical conduit. I bought a ten foot piece at Lowes. With pencil and a three foot length of string, I scribed an arc on a scrap piece of plywood, then built a bending jig.